The present invention is concerned with semiconductor manufacturing equipment, and is more particularly concerned with arrangements for securely holding a substrate while rotating the substrate.
Semiconductor manufacturing generally entails performing a number of processes with respect to a substrate such as a silicon wafer to form integrated circuits on the substrate. For some of the processes it is necessary or desirable to hold the substrate in a horizontal position while rotating the substrate. For this purpose it is known to provide a rotary vacuum-chuck which holds the substrate horizontally on a chuck surface while rotating the substrate. The chuck surface is mounted on a hollow rotary shaft that is coupled to a vacuum generator. The hollow rotary shaft, in turn, is mounted on a rotary junction that includes a seal to maintain vacuum within the shaft. A conventional seal includes a disk that rotates with the shaft and a confronting stationary disk against which the rotary disk rubs.
Problems encountered with conventional seals for rotary vacuum-chucks include a limited useful life due to wear in the seal, and a tendency to generate particles that may contaminate the substrate that is being processed.
The present invention provides for an improved seal for a rotary vacuum-chuck. According to an aspect of the invention, a rotary vacuum-chuck adapted to mount a substrate for rotation is provided. The vacuum-chuck according to this aspect of the invention includes a hollow rotary shaft and a chuck mounted on the hollow rotary shaft and having a surface adapted to support a substrate, the surface having one or more openings in fluid communication with the hollow rotary shaft. Further included is a vacuum generator adapted to evacuate the hollow rotary shaft and the one or more openings. The vacuum-chuck of the invention further includes a labyrinthine gap defined between a first member that rotates with the hollow rotary shaft and a second member that is stationary. A fluid is provided in the labyrinthine gap and is adapted to provide a gas-tight seal between the first member and the second member.
The first member may be integrally formed with the hollow rotary shaft. The vacuum-chuck may further include a fluid recirculation system adapted to provide a flow of fluid in the labyrinthine gap. There may also be included in the vacuum-chuck a temperature control system associated with the fluid recirculation system and adapted to control the temperature of the fluid flowing in the labyrinthine gap. The fluid may be water.
With the vacuum-chuck of the present invention, the number of rubbing parts is reduced, so that the generation of potentially contaminating particles may also be reduced. Moreover, the useful life of the seal at the rotary hollow shaft may be extended, thereby reducing downtime and improving productivity.
Other features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.